Vertical scaling, also known as "scaling up," refers to the process of increasing the capacity of a single server or machine. This can be achieved by adding more resources, such as CPU, RAM, or storage, to enhance its performance. Vertical scaling is often simpler to implement since it involves upgrading existing hardware rather than managing multiple systems. However, vertical scaling has its limitations. There is a maximum capacity that a single machine can reach, and once that limit is hit, further scaling becomes impossible. This contrasts with horizontal scaling, where additional machines are added to distribute the load, allowing for greater flexibility and capacity.